Flue gas processing apparatus and desulfurization method

ABSTRACT

A flue gas processing apparatus for removing sulfur oxide contained in a gas, including a desulfurization tower through which the gas flows, the desulfurization tower including a catalyst unit having at least one activated carbon fiber board which adsorbs the sulfur oxide and a water-supply device configured to supply water to the catalyst unit so as to form sulfuric acid from the sulfur oxide adsorbed to the at least one activated carbon fiber board, the water-supply device being positioned above the catalyst unit in the desulfurization tower, and a pressurizing device configured to apply pressure to the gas supplied to the desulfurization tower so as to flow the gas through the catalyst unit by the pressure.

TECHNICAL FIELD

The present invention relates to a flue gas processing apparatus forremoving sulfur oxides (SO_(x)) contained in a discharge gas generatedby a boiler, a gas turbine, an engine, an incinerator, or a similarfacility combusting a fuel such as coal or heavy oil; and to adesulfurization method for removing sulfur oxides (SO_(x)) contained ina discharge gas.

BACKGROUND ART

Sulfur oxides (SO_(x)) such as sulfur dioxide are contained in dischargegases generated by thermal power stations; plants such aschemical-production plants, metal-processing plants, sintering plants,and paper-making plants; and gas turbines, engines, incinerators, andsimilar facilities provided with a boiler employing a fuel such as coalor heavy oil. Thus, a flue gas processing apparatus is employed in orderto remove SO_(x) contained in discharge gases. Such a conventional fluegas processing apparatus removes SO_(x) contained in a discharge gas, bycausing SO_(x) to be adsorbed by a porous carbon material such asactivated carbon fiber, oxidizing a sulfur component by oxygen containedin the discharge gas in the presence of the porous carbon materialserving as a catalyst unit, and absorbing the oxidation product inwater, to thereby form sulfuric acid, which is removed from the porouscarbon material.

However, the aforementioned conventional flue gas processing apparatusincluding a catalyst unit formed of porous carbon material has theproblem that its processing efficiency is low. In order to solve theproblem, there has been proposed a flue gas processing apparatuscontaining a catalyst unit formed of plate-like activated carbon fibersheets and corrugated activated carbon fiber sheets, which arealternatingly juxtaposed. In the apparatus, water is added dropwise toactivated carbon fiber contained in the catalyst unit, and a dischargegas is caused to pass through conduits provided between the sheets,whereby a sulfur component is effectively removed in the form ofsulfuric acid. However, there remains a demand for further enhancementin processing efficiency of the above flue gas processing apparatus.

In order to meet the demand, an object of the present invention is toprocess sulfur oxides at higher efficiency.

DISCLOSURE OF THE INVENTION

The present invention provides a flue gas processing apparatus includinga catalyst unit formed of at least one activated carbon fiber board, andwater-supply means for supplying, to the catalyst unit, water forforming sulfuric acid, the catalyst unit being provided in the apparatusin the form of a tower through which a discharge gas containing sulfuroxide passes, the water-supply means being provided above the catalystunit or in an upper section of the unit and in the apparatus in the formof a tower, characterized in that the activated carbon fiber boardprovided in the catalyst unit is formed by alternatingly juxtaposing oneor more plate-like activated carbon fiber sheets and one or morecorrugated activated carbon fiber sheets so as to provide verticallyextending conduits, and in that the flue gas processing apparatuscomprises pressurizing means for applying pressure to the discharge gas,to thereby cause the gas to pass through the catalyst unit.

The pressurizing means may be compressing means for compressing thedischarge gas, thereby causing the gas to pass through the catalystunit. In addition, the flue gas processing apparatus may comprisewater-pressurizing means for applying pressure to water for formingsulfuric acid, to thereby supply the water to the catalyst unit. Theflue gas processing apparatus may further comprise another pressurizingmeans; i.e., resistance means for imparting flow resistance to an outletgas discharged from the apparatus in the form of a tower, the resistancemeans being provided in an outlet line for feeding the outlet gasdischarged from the apparatus in the form of a tower. Alternatively, thecatalyst unit may be accommodated in a pressurizing chamber in which adesired pressure is produced, and the discharge gas is caused to passthrough the pressurizing chamber and water is supplied to thepressurizing chamber. In addition, the flue gas processing apparatus mayfurther contain pressure-reducing means for reducing pressure in thepressurizing chamber, to thereby remove fluid contained in the chamber.

The flue gas processing apparatus according to the present invention mayhave, in one or more corrugated activated carbon fiber sheets serving assidewalls of the conduits, at least one hole which allows passage offluid between the conduits.

In the flue gas processing apparatus according to the present invention,the catalyst unit may be formed of a plurality of the activated carbonfiber boards which are vertically disposed.

The present invention provides a desulfurization method includingcausing a discharge gas containing sulfur oxides to pass through acatalyst unit formed of at least one activated carbon fiber board andsupplying water for forming sulfuric acid, characterized by comprisingapplying pressure to the discharge gas, to thereby cause the gas to passthrough the catalyst unit. The desulfurization method further comprisesapplying pressure to the water for forming sulfuric acid, to therebysupply the water.

The present invention also provides a desulfurization method comprisingapplying pressure to a discharge gas containing sulfur oxides, tothereby cause the gas to pass through vertically extending conduitsformed by alternatingly juxtaposing one or more plate-like activatedcarbon fiber sheets and one or more corrugated activated carbon fibersheets forming an activated carbon fiber board provided in a catalystunit, and applying pressure to water for forming sulfuric acid, tothereby supply the water.

The present invention also provides a desulfurization method includingcausing a discharge gas containing sulfur oxides to pass through acatalyst unit formed of at least one activated carbon fiber board andsupplying water for forming sulfuric acid, characterized by comprisingapplying pressure to the catalyst unit, to thereby cause the dischargegas to pass through the catalyst unit, and reducing the pressure appliedto the catalyst unit, to thereby discharge material contained in thecatalyst unit.

The present invention also provides a flue gas processing apparatusincluding a catalyst unit formed of at least one activated carbon fiberboard, and water-supply means for supplying, to the catalyst unit, waterfor forming sulfuric acid, the catalyst unit being provided in theapparatus in the form of a tower through which a discharge gascontaining sulfur oxide passes, the water-supply means being providedabove the catalyst unit or in an upper section of the unit and in theapparatus in the form of a tower, characterized in that the activatedcarbon fiber board provided in the catalyst unit is formed byalternatingly juxtaposing one or more plate-like activated carbon fibersheets and one or more corrugated activated carbon fiber sheets so as toprovide vertically extending conduits, and in that one or morecorrugated activated carbon fiber sheets serving as sidewalls of theconduits have at least one hole which allows passage of the fluidbetween the conduits. The catalyst unit may be formed of a plurality ofthe activated carbon fiber boards which are vertically disposed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system configuration of a discharge gas processing systememploying a flue gas processing apparatus according to one embodiment ofthe present invention.

FIG. 2 is a system configuration of a discharge gas processing systemaccording to another embodiment.

FIG. 3 is a schematic configuration of a desulfurization tower.

FIG. 4 is a perspective view showing a portion of an upper section of anactivated carbon fiber board.

FIG. 5 is a cross-sectional view showing an activated carbon fiberboard.

FIG. 6 is a cross-sectional view showing activated carbon fiber boardsaccording to other embodiments.

FIG. 7 is a cross-sectional view showing an activated carbon fibersheet.

FIG. 8 is a graph showing the relationship between rate of reaction andpressure.

FIG. 9 is a schematic configuration of a desulfurization tower equippedwith pressurizing means according to another embodiment.

FIG. 10 is a schematic configuration of a desulfurization tower equippedwith pressurizing means according to another embodiment.

FIG. 11 is a system configuration of a discharge gas processing systememploying a flue gas processing apparatus according to anotherembodiment of the present invention.

FIG. 12 is an elevation showing an essential portion of an activatedcarbon fiber board of another embodiment for forming the catalyst unit.

FIG. 13 is a perspective view showing a portion of an upper section ofthe activated carbon fiber board.

FIG. 14 is a cross-sectional view showing the activated carbon fiberboard.

FIG. 15 is a cross-sectional view showing activated carbon fiber boardsaccording to other embodiments.

BEST MODES FOR CARRYING OUT THE INVENTION

Best modes for carrying out the present invention will next be describedwith reference to the drawings.

With reference to FIG. 1, a discharge gas process system employing theflue gas processing apparatus according to a first embodiment of thepresent invention will be described. According to the present invention,pressure is applied to the discharge gas to be processed, in order topromote desulfurization reaction.

As shown in FIG. 1, a boiler 1; for example, a boiler for generatingsteam for driving a steam turbine (not illustrated) of a thermal powerplant, combusts fuel f (e.g., coal or heavy oil) in its furnace. Adischarge gas generated from the boiler 1 contains sulfur oxides(SO_(x)). The discharge gas undergoes a NO_(x) removal process by meansof an NO_(x) removal unit (not illustrated), is cooled by means of a gasheater, and subsequently undergoes a soot removal process by means of asoot collector 2.

Pressure is applied to the soot-removed discharge gas by means of acompressor 3 serving as pressurizing means, and the gas is fed to adesulfurization tower 4 serving as a processing apparatus in the form ofa tower, via an inlet 5 provided in a lower section of the tower. Thethus-pressure-elevated discharge gas may be treated in ahumidifying-cooling apparatus 16, where water is added in a sufficientamount, to thereby yield a discharge gas in saturated vapor form. Thethus-humidified discharge gas may contain mist. The desulfurizationtower 4 contains therein a catalyst unit 6 formed of at least oneactivated carbon fiber board, and water for forming sulfuric acid issupplied to the catalyst unit 6 from a water-supplying nozzle 7 providedabove the catalyst unit. Water is supplied from a water tank 8 to thewater-supplying nozzle 7 by use of a pressurizing pump 9 such that thepressure of supplied water is elevated to a suitable pressure determinedin accordance with the pressure of the discharge gas. Water-supply meansincludes the water-supplying nozzle 7, the water tank 8, and the pump 9.

The discharge gas is introduced from the lower section of the tower andcaused to pass through the catalyst unit 6 onto which water has beensupplied, whereby SO_(x) contained in the discharge gas is removedthrough reaction. The discharge gas which has passed through thecatalyst unit 6 is discharged from an outlet 12, and mist contained inthe discharged gas is removed by a mist-eliminator 19, wherebygeneration of white smoke is suppressed. The thus-treated discharge gasis released to the air through a smokestack 13. The mist-eliminator 19may be omitted.

On a surface of the activated carbon fiber board contained in thecatalyst layer 6, desulfurization proceeds in accordance with, forexample, a following reaction mechanism which includes:

-   -   (1) adsorption of sulfur dioxide (SO₂) by the activated carbon        fiber board contained in the catalyst layer 6;    -   (2) oxidation of the adsorbed sulfur dioxide (SO₂) with oxygen        (O₂) (may be supplied separately) contained in the discharge        gas, to thereby form sulfur trioxide (SO₃);    -   (3) dissolution of the resultant sulfur trioxide (SO₃) in water        (H₂O), to thereby form sulfuric acid (H₂SO₄); and    -   (4) release of the resultant sulfuric acid (H₂SO₄) from the        activated carbon fiber board.

The overall reaction is expressed as follows.SO₂+½O₂+H₂O→H₂SO₄

The thus-released sulfuric acid (H₂SO₄) is dilute sulfuric acid and isdischarged into a sulfuric acid tank 11 via a discharge pump 10. Asdescribed above, desulfurization of the discharge gas is performed bycausing, by means of the catalyst unit 6 for oxidation, absorption ofsulfur dioxide (SO₂) contained in the discharge gas, reacting theoxidation product with water (H₂O), to thereby form sulfuric acid(H₂SO₄), and releasing the sulfuric acid from the catalyst unit.

With reference to FIG. 2, a discharge gas processing system according toanother embodiment of the present invention will be described. Herein,the same structural members as employed in the discharge gas processingsystem shown in FIG. 1 are denoted by the same reference numerals, andrepeated descriptions thereof are omitted.

According to the discharge gas processing system shown in FIG. 2, sulfuroxides contained in a discharge gas are removed by means of adesulfurization apparatus, whereby sulfuric acid is formed, and limeslurry is fed to the resultant sulfuric acid, to thereby produce gypsum.

As shown in FIG. 2, the system includes a gypsum reaction tank 52 forstoring dilute sulfuric acid fed from a desulfurization tower 4 via adischarge pump 10 and for depositing gypsum by reaction with suppliedlime slurry 51. In addition, a settling tank 53 is also provided forsettling gypsum deposited in the gypsum reaction tank 52. Gypsum slurry54 formed in the settling tank 53 is transferred to a dewateringapparatus 56, where water is removed from the gypsum slurry, to therebyyield gypsum 55. In the discharge gas processing system shown in FIG. 1,sulfuric acid obtained through desulfurization is used as a sulfuricacid product. However, in the discharge gas processing system shown inFIG. 2, lime slurry 51 is fed to the produced sulfuric acid, therebyforming gypsum slurry 54, followed by dehydration, to thereby yield agypsum product 55.

The structure of the activated carbon fiber board contained in thecatalyst unit 6 will be described with reference to FIGS. 3 to 7.

An activated carbon fiber board 20 is formed by alternatinglyjuxtaposing plate-like activated carbon fiber sheets 21 and corrugated(continuous V-shaped waves) activated carbon fiber sheets 22. Spacesextending straight and provided between two sheets serve as conduits 15,with the conduits 15 extending vertically. The plate-like activatedcarbon fiber sheets 21 and the corrugated activated carbon fiber sheets22 are formed by mixing cotton-form activated carbon fiber (e.g.,pitch-derived or phenol-derived carbon fiber) with a binder and formingthe mixture into a sheet. In the case where the corrugated activatedcarbon fiber sheet 22 is formed, the sheet is worked by use of acorrugator. Subsequently, the thus-formed sheets are heated in anon-oxidizing atmosphere (e.g., nitrogen) at high temperature (e.g.,600° C. to 1,200° C.), to thereby yield activated carbon fiber sheetsfor use in desulfurization. Briefly, a highly hydrophobic surface ofactivated carbon fiber is provided through heat treatment, so as toreadily adsorb sulfur dioxide (SO₂) and rapidly release formed sulfuricacid (H₂SO₄) from activated carbon fiber.

The thus-heat-treated plate-like activated carbon fiber sheets 21 andcorrugated activated carbon fiber sheets 22 are alternatinglyjuxtaposed, and the peak of each corrugated activated carbon fiber sheet22 is joined to the plate-like activated carbon fiber sheet 21 throughmelt adhesion of the binder, to thereby produce a carbon fiber boardmodule of predetermined size. Since the peak of each corrugatedactivated carbon fiber sheet 22 is joined to the plate-like activatedcarbon fiber sheet 21 through melt adhesion of the binder, no additionaladhesive, such as an organic substance, is used. Thus, adverse effect ofthe adhesive on desulfurization reaction is eliminated, and reliabilityof joining is enhanced, thereby eliminating the effect of pressure loss.

In one mode, four modules of the activated carbon fiber board 20 arejuxtaposed such that the conduits 15 are disposed vertically, to therebyyield one unit. Two units are stacked, and the stacked units are placedand immobilized in a casing. Briefly, a plurality of activated carbonfiber boards 20 are disposed and stacked in a vertical direction, tothereby provide the catalyst unit 6. Thus, the size of each activatedcarbon fiber board 20 can be reduced, thereby facilitating assembly ofthe catalyst unit.

As shown in FIG. 4, the pitch p between plate-like activated carbonfiber sheets 21 is predetermined to be, for example, approximately 4 mm,and the width h of each protruded portion of the corrugated activatedcarbon fiber board 22 is predetermined to be, for example, approximately10 mm. From a position above the activated carbon fiber boards, water issprayed thereonto in the form of droplets approximately 200 μm in size,and a discharge gas is introduced from a position below the activatedcarbon fiber boards. Water which has passed through the activated carbonfiber boards 20 falls, in the form of droplets of about some mm in size,to the bottom of the desulfurization tower 4. The discharge gas passesthrough conduits 15 provided by alternatingly juxtaposing the plate-likeactivated carbon fiber sheets 21 and corrugated activated carbon fibersheets 22. Thus, an increase in pressure loss can be suppressed.

SO₃ formed through oxidation of SO₂ on the surface of activated carbonfiber is transformed into sulfuric acid by water, and the sulfuric acidis discharged. When the amount of water is insufficient, discharge ofsulfuric acid cannot be attained and subsequent oxidation of SO₂ isinsufficient, whereas when the amount of water is excessive, the yieldedsulfuric acid is diluted. Furthermore, when the amount of water furtherincreases; for example, in the case where the activated carbon fiber iscovered with a thin layer or a wall of water which covers active sitesof the activated carbon fiber, such activated carbon fiber losescatalytic action of oxidizing SO₂, thereby failing to attaindesulfurization or deteriorating desulfurization efficiency.

Therefore, the amount of water supplied when a discharge gas comes intocontact with the activated carbon fiber boards 20 contained in thecatalyst unit 6 is predetermined such that water is sprayed thereonto inthe form of droplets of approximately 200 μm in size from a positionabove the activated carbon fiber boards 20, and such that water whichhas passed through the activated carbon fiber boards 20 falls, in theform of droplets of about some mm in size, to the bottom of thedesulfurization tower 4. Accordingly, water falls intermittently in theform of spherical droplets, although falling conditions depend on theconditions of the discharge gas. Thus, water can be supplied to thesurface of activated carbon fiber in a sufficient, yet not excessiveamount, and sulfuric acid can be released at high efficiency. As aresult, desulfurization of a discharge gas can be effectively performed.

As shown in FIG. 6(A), the corrugated activated carbon fiber sheet 31may be formed so as to have a continuous U-shape pattern, and aplurality of the corrugated activated carbon fiber sheets 31 andplate-like activated carbon fiber sheets 21 are alternatingly juxtaposedsuch that the U-shape patterns are oriented in the same direction.Alternatively, as shown in FIG. 6(B), a plurality of the corrugatedactivated carbon fiber sheets 31 and plate-like activated carbon fibersheets 21 are alternatingly juxtaposed such that the orientation of theU-shape pattern is alternatingly disposed. Alternatively, as shown inFIG. 6(C), minute raised/dented patterns 32 may be provided in thesurface of the corrugated activated carbon fiber sheets 31.

As illustrated in FIG. 7, a plate-like activated carbon fiber sheet 21and corrugated activated carbon fiber sheets 22 and 31 are produced bytightly attaching a fired carbon sheet 35 on each side of a corematerial 34, to thereby form a laminated board. The core material 34 maybe omitted.

As shown in FIG. 3, the discharge gas is compressed by a compressor 3,and the thus-pressure-elevated gas is fed from an inlet 5 into adesulfurization tower 4. The discharge gas is distributed by means of adistributor 42, and the distributed gas is fed to a catalyst unit 6. Thepressure of water supplied from a water tank 8 is elevated by use of apressurizing pump 9 serving water-pressurizing means such that thepressure of water supplied from a water-supplying nozzle 7 is elevatedto a suitable pressure determined in accordance with the pressure of thedischarge gas. Thus, desulfurization is performed while pressure of thedischarge gas and water passing through activated carbon fiber board 20is elevated. In addition, the compressor 3 for compressing discharge gasfacilitates elevating pressure of the discharge gas.

The desulfurization tower 4 has an air-tight structure such that thepressure of discharge gas and that of water are maintained.

As shown in FIG. 8, rate of reaction (i.e., amounts of adsorbed sulfurdioxide (SO₂) and oxygen (O₂)) increases as pressure of the fluidpassing through the activated carbon fiber boards 20 is elevated. Thus,adsorption of sulfur dioxide (SO₂) and oxygen (O₂) onto the activatedcarbon fiber board 20 can be promoted. In other words, the amounts ofadsorbed sulfur dioxide (SO₂) and oxygen (O₂) can be increased withoutincreasing the surface area (i.e., size) of the activated carbon fiberboard 20.

Accordingly, there can be provided a flue gas processing apparatushaving the catalyst unit 6 formed of at least one activated carbon fiberboard 20, wherein adsorption of sulfur components is promoted, therebyelevating desulfurization efficiency.

With reference to FIG. 9, pressurizing means according to anotherembodiment of the present invention will be described. FIG. 9 shows theschematic configuration of a desulfurization tower equipped withpressurizing means according to another embodiment. Herein, the samemembers as shown in FIG. 3 are denoted by the same reference numerals,and repeated descriptions thereof are omitted.

As shown in FIG. 9, the discharge gas from which soot has been removedby means of a soot-collector 2 (see FIGS. 1 and 2) is fed to adesulfurization tower 4 from an inlet 5 by means of a feed pump 25.Water is fed from a water tank 8 to a water-supplying nozzle 7 by meansof a pump 26. The discharge gas and water are caused to pass through anactivated carbon fiber board 20, whereby desulfurization is performed.

In an outlet line 27 connecting an outlet 12 with a mist-eliminator 19(see FIGS. 1 and 2), a restriction member 28 serving as resistance meansis provided, whereby flow resistance is imparted to the discharge gasfed from the outlet line 27. Since the discharge gas is continuously fedinto the desulfurization tower 4 by means of the feed pump 25, internalpressure of the desulfurization tower 4 gradually increases when thedischarge gas is imparted with flow resistance by the restriction member28, whereby pressure-elevated discharge gas and water are supplied.Thus, desulfurization is performed while pressure of the discharge gasand water passing through activated carbon fiber board 20 is elevated.According to this embodiment, the internal pressure of thedesulfurization tower 4 is increased through provision of therestriction member 28. Therefore, pressure can be applied to thedischarge gas and water without employment of special driving means.

Thus, adsorption of sulfur dioxide (SO₂) and oxygen (O₂) onto theactivated carbon fiber board 20 can be promoted. In other words, theamounts of adsorbed sulfur dioxide (SO₂) and oxygen (O₂) can beincreased without increasing the size of the activated carbon fiberboard 20.

Accordingly, there can be provided a flue gas processing apparatushaving the catalyst unit 6 formed of at least one activated carbon fiberboard 20, wherein adsorption of sulfur components is promoted, therebyelevating desulfurization efficiency.

With reference to FIG. 10, pressurizing means according to anotherembodiment of the present invention will be described. FIG. 10 shows theschematic configuration of a desulfurization tower equipped withpressurizing means according to another embodiment. Herein, the samemembers as shown in FIG. 3 or 9 are denoted by the same referencenumerals, and repeated descriptions thereof are omitted.

As shown in FIG. 10, a desulfurization tower 4 includes a pressurizingchamber 38 whose internal pressure is elevated to a predetermined levelby pressurizing means 37. The pressurizing chamber 38 accommodates acatalyst unit 6 containing an activated carbon fiber board 20. To thepressurizing chamber 38, a pressure-reducing line 39 is connected. Apressure-reducing valve 40 is provided in the pressure-reducing line 39.The pressure-reducing line 39 establishes its communication when thepressure-reducing valve 40 opens, whereby the internal pressure of thepressurizing chamber 38 is reduced.

The discharge gas from which soot has been removed by means of asoot-collector 2 (see FIGS. 1 and 2) is fed to the desulfurization tower4 from an inlet 5 by means of a feed pump 25. The discharge gas fed intothe tower is introduced into the pressurizing chamber 38 via a guidemember (not illustrated). Water is fed from a water tank 8 to awater-supplying nozzle 7 by means of a pump 26. The water is introducedfrom the water-supplying nozzle 7 into the pressurizing chamber 38 via aguide member (not illustrated). The discharge gas and water are causedto pass through an activated carbon fiber board 20 accommodated in thepressurizing chamber 38, whereby desulfurization is performed underpressure application. The gas which has been desulfurized is removedfrom the pressurizing chamber 38.

Thus, adsorption of sulfur dioxide (SO₂) and oxygen (O₂) onto theactivated carbon fiber board 20 can be promoted. In other words, theamounts of adsorbed sulfur dioxide (SO₂) and oxygen (O₂) can beincreased without increasing the size of the activated carbon fiberboard 20. In addition, application of pressure to the discharge gas andwater can be ensured through provision of the pressurizing chamber 38.

Accordingly, there can be provided a flue gas processing apparatushaving the catalyst unit 6 formed of at least one activated carbon fiberboard 20, wherein adsorption of sulfur components is promoted, therebyelevating desulfurization efficiency.

When the pressure-reducing valve 40 is opened at an appropriate timing,to thereby reduce the pressure in the pressurizing chamber 38, fluid andmicro-particles contained in the pressurizing chamber 38 are forcedlyremoved through the pressure-reducing line 39. Thus, undesired mist andmicro-particles clogging the activated carbon fiber board 20 can beremoved. When the pressure-reducing valve 40 is periodically opened soas to reduce the pressure in the pressurizing chamber 38, clogging ofthe activated carbon fiber board 20 can be prevented.

The compressor 3 or the pressurizing pump 9 shown in FIG. 3 may beprovided instead of the feed pump 25 or the pump 26.

According to the aforementioned flue gas processing apparatus,pressure-elevated discharge gas and water are caused to pass through thecatalyst unit 6. Thus, there can be provided a flue gas processingapparatus having the catalyst unit 6 formed of at least one activatedcarbon fiber board, wherein adsorption of sulfur components is promoted,thereby elevating desulfurization efficiency. According to theaforementioned desulfurization method, pressure is applied to dischargegas and water, to thereby cause the discharge gas and water to passthrough the catalyst unit 6. Thus, there can be provided adesulfurization method wherein adsorption of sulfur components ispromoted, thereby effectively removing sulfur oxides (SO_(x)).

The present invention provides a flue gas processing apparatus includinga catalyst unit formed of at least one activated carbon fiber board, andwater-supply means for supplying, to the catalyst unit, water forforming sulfuric acid, the catalyst unit being provided in the apparatusin the form of a tower through which a discharge gas containing sulfuroxide passes, the water-supply means being provided above the catalystunit or in an upper section of the unit and in the apparatus in the formof a tower, characterized in that the activated carbon fiber boardprovided in the catalyst unit is formed by alternatingly juxtaposing oneor more plate-like activated carbon fiber sheets and one or morecorrugated activated carbon fiber sheets so as to provide verticallyextending conduits, and in that the flue gas processing apparatuscomprises pressurizing means for applying pressure to the discharge gas,to thereby cause the gas to pass through the catalyst unit. Thus, thepressure-elevated discharge gas is desulfurized by causing the gas topass through the catalyst unit. As a result, adsorption of sulfurcomponents is promoted, thereby effectively performing desulfurization.

When the pressurizing means is compressing means for compressing thedischarge gas, to thereby cause the gas to pass through the catalystunit, pressure can be readily applied to the discharge gas.

When the flue gas processing apparatus includes water-pressurizing meansfor applying pressure to the water for forming sulfuric acid, to therebysupply the water to the catalyst unit, the pressure-elevated dischargegas is desulfurized by causing the gas to pass through the catalyst unitto which pressure-elevated water is supplied.

When the pressurizing means is resistance means for imparting flowresistance to a discharged outlet gas, the resistance means beingprovided in an outlet line for feeding the outlet gas discharged fromthe apparatus in the form of a tower, pressure can be applied to thedischarge gas without employment of special driving means.

When the catalyst unit is accommodated in a pressurizing chamber forapplying desired pressure, and the discharge gas is caused to passthrough the pressurizing chamber and water is supplied to thepressurizing chamber, application of pressure to the discharge gas andwater can be ensured.

When the flue gas processing apparatus further containspressure-reducing means for reducing pressure in the pressurizingchamber, to thereby remove fluid contained in the chamber,micro-particles or similar substances contained in the pressurizingchamber can be also removed, to thereby prevent clogging of the catalystunit.

The present invention provides a desulfurization method includingcausing a discharge gas containing sulfur oxides to pass through acatalyst unit formed of at least one activated carbon fiber board andsupplying water for forming sulfuric acid, characterized by comprisingapplying pressure to the discharge gas, to thereby cause the gas to passthrough the catalyst unit. Therefore, adsorption of sulfur components ispromoted, thereby effectively removing sulfur oxides. The presentinvention also provides a desulfurization method comprising applyingpressure to a discharge gas, to thereby cause the gas to pass throughvertically extending conduits formed by alternatingly juxtaposing one ormore plate-like activated carbon fiber sheets and one or more corrugatedactivated carbon fiber sheets forming an activated carbon fiber boardprovided in a catalyst unit, and applying pressure to water for formingsulfuric acid, to thereby supply the water. Therefore, adsorption ofsulfur components is promoted, thereby effectively removing sulfuroxides.

When pressure is applied to the water for forming sulfuric acid, tothereby supply the water, pressure can be applied to both the dischargegas and water.

The present invention also provides a desulfurization method includingcausing a discharge gas containing sulfur oxides to pass through acatalyst unit formed of at least one activated carbon fiber board andsupplying water for forming sulfuric acid, characterized by comprisingapplying pressure to the catalyst unit, to thereby cause the dischargegas to pass through the catalyst unit, and reducing the pressure appliedto the catalyst unit, to thereby discharge material contained in thecatalyst unit. Thus, there can be provided a desulfurization methodwhich promotes adsorption of sulfur components, thereby effectivelyremoving sulfur oxides, and which can remove fluid, micro-particles, orsimilar substances, to thereby prevent clogging of the catalyst unit.

With reference to FIG. 11, a flue gas processing apparatus according toanother embodiment of the present invention will be described. Accordingto this embodiment, supplied water is allowed to be present evenly overthe catalyst unit so as to enhance desulfurization efficiency.

FIG. 11 shows a discharge gas processing system employing a flue gasprocessing apparatus according to another embodiment of the presentinvention, and the essential structure thereof is the same as shown inFIG. 1. Specifically, as shown in FIG. 11, a boiler 1; for example, aboiler for generating steam for driving a steam turbine (notillustrated) of a thermal power plant, combusts fuel f (e.g., coal orheavy oil) in its furnace. A discharge gas generated from the boiler 1contains sulfur oxides (SO_(x)). The discharge gas undergoes a NO_(x)removal process by means of an NO_(x) removal unit (not illustrated), iscooled by means of a gas heater, and subsequently undergoes a sootremoval process by means of a soot collector 2.

The soot-removed discharge gas is fed, by means of a feed fan 103, to ahumidifying-cooling apparatus 16, where water (including dilute sulfuricacid) is added, to thereby yield a discharge gas in saturated vaporform. The thus-humidified discharge gas may contain mist. The dischargegas in saturated vapor form produced in the humidifying-coolingapparatus 16 is fed to a desulfurization tower 4 (desulfurizationapparatus in the form of a tower) via an inlet 5 provided in a lowersection of the tower. The desulfurization tower 4 contains a catalystunit 6 formed of at least one activated carbon fiber board, and waterfor producing sulfuric acid is supplied to the catalyst unit 6 from awater-supplying nozzle 7 provided above the catalyst unit. Water issupplied to the water-supplying nozzle 7 from a water tank 8 by use of apump 9. Water-supply means includes the water-supplying nozzle 7, thewater tank 8, and the pump 9.

The discharge gas is introduced from the lower section of the tower andcaused to pass through the catalyst unit 6 onto which water has beensupplied, whereby SO_(x) contained in the discharge gas is removedthrough reaction. The discharge gas which has passed through thecatalyst unit 6 is discharged from an outlet 12, and mist contained inthe discharged gas is removed by a mist-eliminator 19, wherebygeneration of white smoke is suppressed. The thus-treated discharge gasis released to the air through a chimney 13. The mist-eliminator 19 maybe omitted.

On a surface of the activated carbon fiber board contained in thecatalyst layer 6, desulfurization proceeds in accordance with theaforementioned reaction mechanism.

Similar to the case of the embodiment described with reference to FIG.1, according to the system of the present embodiment, sulfur oxidescontained in a discharge gas are removed by means of a desulfurizationapparatus, whereby sulfuric acid is formed. The thus-released sulfuricacid (H₂SO₄) is dilute sulfuric acid and is discharged into a sulfuricacid tank 11 via a discharge pump 10. Also, as described with referenceto FIG. 2 lime slurry may be fed to the resultant sulfuric acid, tothereby produce gypsum. The effects and action of the system are thesame as described above.

The structure of the activated carbon fiber board contained in thecatalyst unit 6 employed in the present embodiment will be describedwith reference to FIGS. 12 to 15.

The essential structure of an activated carbon fiber board 120 is thesame as shown in FIGS. 4 to 7, and the same members thereof are denotedby the same reference numerals. Thus, repeated descriptions thereof areomitted.

In the activated carbon fiber board 120, a large number of narrowconduits 15 are individually provided. Water for producing sulfuric acidis supplied to each conduit 15 from a position above the correspondingconduit 15, while a discharge gas is supplied from a lower section ofthe catalyst unit. Thus, when the pressure of water supplied from theupper position and that of the discharge gas supplied from the lowersection are equilibrated, a water membrane 40 is formed in some conduits15, thereby possibly clogging the corresponding conduits 15, as shown inFIGS. 14 and 15. Although clogging of the conduits 15 can be preventedby suppressing formation of the water membrane 40 through widening ofthe conduits 15, contact area between the surface of the activatedcarbon fiber board 120 and the discharge gas decreases, thereby failingto attain desired catalytic efficiency within a limited space.

In order to overcome the above drawback, as shown in FIGS. 12 to 15,holes 18 which allow passage of water and discharge gas between theconduits 15 are provided in sidewalls (corrugated activated carbon fibersheets 22 and 31) forming the conduits 15 formed in the activated carbonfiber board 120. At least one (three in the case of FIG. 12) hole 18 isprovided in the direction of flow in each conduit 15 (fluid flowdirection), and the holes 18 are provided in a plurality of conduits 15such that passage of water and discharge gas can be attained from oneconduit 15 to all adjacent conduits 15.

Since a plurality of holes 18 are provided in each conduit 15 in thefluid flow direction, passage of water and discharge gas between theconduits 15 is ensured, even when the amount (weight) of supplied wateror pressure of supplied discharge gas is not constant. In addition,since holes 18 are provided such that communication can be attained fromone conduit 15 to all adjacent conduits 15, passage of water anddischarge gas between the conduits 15 is ensured, even when the amount(weight) of water contained in the activated carbon fiber board 120 orpressure of supplied discharge gas passing through the activated carbonfiber board 120 is not evenly provided.

In the flue gas processing apparatus employing the aforementionedcatalyst unit 6, holes 18 are provided in sidewalls of the conduits 15formed in the activated carbon fiber board 120 included in the catalystunit 6. Thus, even when the weight of water supplied from a positionabove the conduits and pressure of the discharge gas supplied from thelower section are equilibrated, the discharge gas (or water) passingthrough one conduit flows, via the holes 18, into another conduit 15 oflower pressure. As a result, decrease in pressure of the discharge gasallows falling of water, thereby preventing formation of the watermembrane 40 in the conduits 15. Thus, inhibition of flow of thedischarge gas caused by clogging of the conduits 15 is prevented,thereby attaining even flow of water and the discharge gas over theentirety of the activated carbon fiber board 120.

When the catalyst unit 6 is formed of a plurality of activated carbonfiber boards 120, which are vertically disposed, water is evenlysupplied in a lower activated carbon fiber board 120, and the dischargegas is evenly supplied to an upper activated carbon fiber board 120.Through provision of such holes, even when the catalyst unit 6 is formedof a plurality of stages of activated carbon fiber boards 120, water andthe discharge gas can be uniformly dispersed, thereby eliminatingadverse effects on sulfur dioxide (SO₂) removal efficiency.

Thus, there can be provided a catalyst unit 6 having an activated carbonfiber board 120 in which water is evenly distributed, the catalyst unitallowing passage of the discharge gas without inhibition of flow undersmall pressure loss conditions. Even when narrower conduits 15 areprovided; i.e., when contact area between the fluid and the activatedcarbon fiber board 120 increases, favorable flow conditions of thedischarge gas can be maintained, and decrease in desulfurizationefficiency can be prevented by evenly distributing water.

The flue gas processing apparatuses according to the aforementionedembodiments have been described in relation to the case where thedischarge gas is fed from a lower section of the desulfurization tower 4and discharged in the upper direction. However, no particular limitationis imposed on the positions of the inlet and the outlet, and there maybe employed a mode of flow in which the discharge gas is fed from thetop of the desulfurization tower 4 and discharged from a lower sectionthereof.

The present invention also provides a flue gas processing apparatusincluding a catalyst unit formed of at least one activated carbon fiberboard, and water-supply means for supplying, to the catalyst unit, waterfor forming sulfuric acid, the catalyst unit being provided in theapparatus in the form of a tower through which a discharge gascontaining sulfur oxide passes, the water-supply means being providedabove the catalyst unit or in an upper section of the unit and in theapparatus in the form of a tower, characterized in that the activatedcarbon fiber board provided in the catalyst unit is formed byalternatingly juxtaposing one or more plate-like activated carbon fibersheets and one or more corrugated activated carbon fiber sheets so as toprovide vertically extending conduits, and in that one or more sidewallsforming the conduits; i.e., the corrugated activated carbon fibersheets, have at least one hole which allows passage of the fluid betweenthe conduits. With the above structure, even when pressure of water andpressure of the discharge gas are equilibrated, the discharge gas (orwater) passing through one conduit flows, via the holes, into anotherconduit of lower pressure. Thus, inhibition of flow of the discharge gascaused by clogging of the conduits is prevented, thereby attaining evenflow of water and the discharge gas over the entirety of the activatedcarbon fiber board. As a result, there can be provided a flue gasprocessing apparatus employing a catalyst unit formed of at least oneactivated carbon fiber board, the catalyst unit allowing passage of thedischarge gas without inhibition of flow under even water distributionand small pressure loss conditions.

Since at least one hole is provided in each conduit in the fluid flowdirection, passage of water and discharge gas between the conduits isensured, even when the amount (weight) of water or pressure of supplieddischarge gas is not constant.

In addition, since holes are provided such that communication can beattained from one conduit to all adjacent conduits, passage of water anddischarge gas between the conduits is ensured, even when the pressure ofwater contained in the activated carbon fiber board or pressure ofsupplied discharge gas passing through the activated carbon fiber boardis not evenly distributed.

When a catalyst unit is formed of a plurality of activated carbon fiberboards disposed and stacked in a vertical direction, the size of eachactivated carbon fiber board can be reduced, thereby facilitatingassembly of the catalyst unit.

The catalyst units 6 contained in the desulfurization apparatus 4employed in the embodiments shown in FIGS. 1, 2, 9, and 10 may bereplaced by any one of the activated carbon fiber boards 120 shown inthe FIGS. 12 to 14 and 15. According to such embodiments, pressure isapplied to the discharge gas to be fed to the catalyst unit, and thedischarge gas is allowed to flow between the conduits.

According to these embodiments, desulfurization is performed by causingthe pressure-elevated discharged gas to pass through the catalyst unit,and adsorption of sulfur components is promoted, thereby effectivelyperforming desulfurization. In addition, since holes which allow passageof fluid between conduits are provided in sidewalls forming conduits ofthe activated carbon fiber board, even when the pressure of water andpressure of the discharge gas are equilibrated, the discharge gas (orwater) passing through one conduit flows, via the holes, into anotherconduit of lower pressure. Thus, inhibition of flow of the discharge gascaused by clogging of the conduits is prevented, thereby attaining evenflow of water and the discharge gas over the entirety of the activatedcarbon fiber board. As a result, the discharge gas can be caused to passwithout inhibition of flow under even water distribution and smallpressure loss conditions.

INDUSTRIAL APPLICABILITY

As described hereinabove, the flue gas processing apparatus and theprocessing method according to the present invention can remove sulfuroxides contained in discharge gas efficiently. Thus, the apparatus andmethod are suitable for processing discharge gas generated by a boiler,a gas turbine, an engine, a combustion furnace, or a similar facilitycombusting a fuel such as coal or heavy oil.

1. A desulfurization method for a gas containing sulfur oxide,comprising: providing a catalyst unit including at least one activatedcarbon fiber board which adsorbs the sulfur oxide; supplying water tothe catalyst unit so as to form sulfuric acid from the sulfur oxide; andapplying pressure to the gas so as to flow the gas through the catalystunit.
 2. The desulfurization method according to claim 1, wherein theproviding comprises providing the catalyst unit in a pressurizingchamber in which a pressure is applied to the gas passing through thepressurizing chamber and to the water supplied to the pressurizingchamber, and the pressure is higher than a pressure outside thepressurizing chamber.
 3. A desulfurization method for a gas containingsulfur oxide, comprising: providing a catalyst unit including anactivated carbon fiber board to which the sulfur oxide is adsorbed, theactivated carbon fiber board having at least one activated carbon fibersheet and at least one corrugated activated carbon fiber sheetpositioned alternately in juxtaposition to form vertically extendingconduits; applying pressure to the gas so as to flow the gas through thevertically extending conduits applying pressure to water so as to supplythe water to the catalyst unit.
 4. The desulfurization method accordingto claim 3, wherein the pressure is applied to the water so as to formsulfuric acid from the sulfur oxide adsorbed to the activated carbonfiber board.
 5. A desulfurization method for a gas containing sulfuroxide, comprising: providing a catalyst unit including at least oneactivated carbon fiber board which adsorbs the sulfur oxide; supplyingwater to the catalyst unit so as to form sulfuric acid; from the sulfuroxide adsorbed to the at least one activated carbon fiber board;applying pressure to the catalyst unit so as to flow the gas through thecatalyst unit by the pressure; and reducing the pressure applied to thecatalyst unit so as to discharge material contained in the catalystunit.
 6. A flue gas processing apparatus for removing sulfur oxidecontained in a gas, comprising: a desulfurization tower through whichthe gas flows, the desulfurization tower including a catalyst unithaving at least one activated carbon fiber board which adsorbs thesulfur oxide and a water-supply device configured to supply water to thecatalyst unit so as to form sulfuric acid from the sulfur oxide adsorbedto the at least one activated carbon fiber board, the water-supplydevice being positioned above the catalyst unit in the desulfurizationtower; and a pressurizing device configured to apply pressure to the gassupplied to the desulfurization tower so as to flow the gas through thecatalyst unit by the pressure, wherein the at least one activated carbonfiber board has at least one activated carbon fiber sheet and at leastone corrugated activated carbon fiber sheet positioned alternately injuxtaposition so as to provide conduits extending vertically.
 7. Theflue gas processing apparatus according to claim 6, wherein thepressurizing device includes a compressing device configured to compressthe gas, thereby causing the gas to pass through the catalyst unit. 8.The flue gas processing apparatus according to claim 7, furthercomprising a water-pressurizing device configured to apply pressure tothe water so as to supply the water to the catalyst unit.
 9. The fluegas processing apparatus according to claim 6, wherein the catalyst unitis positioned in a pressurizing chamber in which a pressure is appliedto the gas passing through the pressurizing chamber and to the watersupplied to the pressurizing chamber, and the pressure is higher than apressure outside the pressurizing chamber.
 10. The flue gas processingapparatus according to claim 9, wherein the pressurizing chamberincludes a pressure reducing device configured to reduce the pressure inthe pressurizing chamber so as to remove fluid contained in thepressurizing chamber.
 11. The flue gas processing apparatus according toclaim 6, wherein the desulfurization tower has an outlet line throughwhich the gas is discharged, and the pressurizing device includes aresistance device configured to impart flow resistance to the gasdischarged from the desulfurization tower.
 12. The flue gas processingapparatus according to claim 6, wherein the at least one corrugatedactivated carbon fiber sheet has at least one hole which allows passageof fluid between the conduits.
 13. The flue gas processing apparatusaccording to claim 6, wherein the at least one activated carbon fiberboard includes a plurality of activated carbon fiber boards which arevertically disposed.
 14. A flue gas processing apparatus for removingsulfur oxide contained in a gas, comprising: a desulfurization towerthrough which the gas flows, the desulfurization tower including acatalyst unit having at least one activated carbon fiber board whichadsorbs the sulfur oxide, and a water-supply device configured to supplywater to the catalyst unit so as to form sulfuric acid from the sulfuroxide adsorbed to the at least one activated carbon fiber board, thewater-supply device being positioned in an upper section of thedesulfurization tower; and a pressurizing device configured to applypressure to the gas so as to flow the gas through the catalyst unit bythe pressure, wherein the at least one activated carbon fiber boardincludes at least one activated carbon fiber sheet and at least onecorrugated activated carbon fiber sheet positioned so as to provideconduits extending vertically, and the at least one corrugated activatedcarbon fiber sheet has at least one hole which allows passage of fluidbetween the conduits.
 15. The flue gas processing apparatus according toclaim 14, wherein the at least one activated carbon fiber board includesa plurality of activated carbon fiber boards which are verticallydisposed.
 16. An apparatus for removing sulfur oxide contained in a gas,comprising: a catalyst unit having at least one activated carbon fiberboard which adsorbs the sulfur oxide; a water-supply device configuredto supply water to the catalyst unit so as to form sulfuric acid fromthe sulfur oxide adsorbed to the at least one activated carbon fiberboard; and a pressurizing device configured to apply pressure to the gasso as to flow the gas through the catalyst unit by the pressure.
 17. Anapparatus for removing sulfur oxide contained in a gas, comprising: adesulfurization tower through which the gas flows, the desulfurizationtower including a catalyst unit having at least one activated carbonfiber board which adsorbs the sulfur oxide and a water-supply deviceconfigured to supply water to the catalyst unit so as to form sulfuricacid from the sulfur oxide adsorbed to the at least one activated carbonfiber board, the water-supply device being positioned above the catalystunit in the desulfurization tower; and pressurizing means for applyingpressure to the gas so as to flow the gas through the catalyst unit bythe pressure, wherein the at least one activated carbon fiber board hasat least one activated carbon fiber sheet and at least one corrugatedactivated carbon fiber sheet positioned alternately in juxtaposition soas to provide conduits extending vertically.